Precision spindle for grinding wheels and the like



ROLLIWMSEVERANCE June 10, 1941.

R. M. SEVERANC'E PRECISION SPINDLE FOR GRINDiNG WHEELS AND THE LI FiledMarch 15, 1939 A BN m N\ S] m mm H l1 4. w .QQQENQQ n m 5, x. ax. w 59 Qw MN AWN INVENTOR ATTORNEY.

Patented June 10, 1941 PRECISICN SPINDLE FOR GRINDING WHEELS AND THELIKE l tollin Severance, Saginaw, Mich.

Application March 15, 1939, Serial No. 261,900

' 1 Claim.

This invention relates to grinding machines and pertains moreparticularly to a precision spindle mounting device for grinding wheelsused in certain classes of work that require extreme wheel accuracy forthe rapid removal of metal from a work piece and for giving maximumdurability to the grinding wheel.

Correct appreciation of the novelty and advantages in use of my presentimprovement requires a brief explanation of well-known characteristicswhich attend the use of grinding wheels in devices of the character towhich this invention is especially adaptable.

In the mass production of milling cutters, drills, reamers and the likethe work piece is held'by means of automatic profiling appliances, butsuch equipment is very expensive and is economical only when used inmass production of identical parts.

There is an extensive field wherein relatively small numbers of specialshaped tools are required that can not be made economically on machinesequipped with automatic work holding and guiding devices.

Special shaped tools in small lots must be made on less expensivemachines, the work being guided and directed by the operators hands asin diamond cutting, and gauged by his eyesight with the aid of amagnifying glass. My present improvement is especially adapted to dothat class of work. At first small diameter grinding Wheels are used.They were made very hard, and proved unsatisfactory principally becausetheir rate of removal of metal from the WOIk piece was too slow. It wasfound by experiment and research that for best cutting results theparticles of abrasive should Wear away from the Wheel continually duringthe work so as to keep presenting a fresh grinding surface. Softerwheels were tried and gave somewhat better rates of metal removal, butsoft wheels had the serious disadvantage that they would get slightlyout of true and as soon as they commenced to wabble, run unevenly, orwaver even slightly in their plane of rotation excessive wear wouldoccur on the wheel itself. This was probably because even the minutestfraction of an inch of wabble or wavering results in bringing thegrinding face of the tool into contact with the work piece at intervalsduring the rotation of the wheel, instead of being in contact all thetime, and the result of that action was of course to wear the surface ofthe wheel out of true and aggravate the depreciation of the wheel. Fromthe standpoint of toolproduction this was a serious defeet because itwas necessary to stop production and dress the wheel as soon as even aslight erratic wheel action occurred. Thus, along with the advantage ofusing a soft wheel there developed a disadvantage of not having a wheelmounting that would show a sufficiently high degree of sustainedaccuracy and durability.

My improvement provides such a mounting in a highly satisfactory mannerand the device herein described and claimed accomplishes the objects ofthe invention which are, to provide a mounting for a grinding wheel thatwill keep the axis of the wheel in a fixed line while running and willprevent any movement of the wheel or its spindle in a directionlengthwise of the axis; to provide such a bearing arrangement for thewheel spindle that will in addition permit the bearing nearest the wheelto be adjusted to take up wear on the peripheral rubbing surfaces of thebearing, and to provide means for holding the wheel against endwisemovement, both adjustments being attained by merely turning theappropriate screw threaded members on the housing of the spindle andwithout dismantling the wheel supporting structure.

Another object is to provide a simplified device for effecting theadjustments above mentioned by means of spindle bearings only.

With the foregoing and certain other objects in view which will appearlater in the specification, my invention comprises the devices describedand claimed and the equivalents thereof.

In the drawing,

Fig. 1 is a cross-sectional side view of a grinding wheel and spindlemounted on a housing embodying my improvement;

Fig. 2 is a perspective View of the rear bear- Fig. 3 is a sectionalview of the rear cap; and

Fig. 4 is a sectional View of the front cap.

Referring now to Fig. l, the grinding Wheel I is located between a pairof center flanges 2, 3 on the threaded end 4 of the spindle and issecured by means of a nut 5 in the usual way. On the spindle is atapered journal 6, its larger end being nearest the wheel. Betweenjournal 6 and wheel I and integral with the spindle is an outwardlyprojecting circular flange or collar 1.

The tapered journal 6, the collar 1, the grinding wheel I, therespective bearings in which journal 6 and collar 1 run and the meansfor adjusting these bearings in their co-operative relationship,constitutes an important feature of my improvement, as will be explainedin detail later.

At the end of the spindle remote from the wheel I, being the left-handend in Fig. 1, is a journal 8 cylindrical in form, running in a rearbearing 9, which bearing is longitudinally split so as to be adjustablefor taking up wear of the cylindrical running faces.

Gbserving now the mounting of tapered journal 6, Fig. 1, it is seen thatthe journal rotates in a correspondingly tapered bushing H) of antifriction metal secured by a press fit in the counterbore H of a tubularhousing I2.

But the rear bearing 9 for journal 3 is bored cylindrically and as shownin Fig. 2, the outer tapered surface of the bearing 9 is flutedperipherally by grooves 13 that extend longitudinally. The groovesimpart a degree of peripheral yield to the bearing for adjusting itstightness on the journal 9. A longitudinal split 54 is provided for thesame purpose.

The rear bushing 9 has endwise adjustment in a tapered fitting [5 whichis mounted by a press fit in a counterbore 46 at the rear end of housing52. Thus the spindle is rotatably mounted in the housing so that itstapered journal 6 rotates in bushing H].

To maintain the necessary accuracy of fit between journal in and itsbushing HI, I have provided a simplified and dependable means foradjusting those parts relatively to each other and for keeping them inproper running relation.

To hold the tapered journal 6 against movement lengthwise I providecollar 1 integral with the spindle between journal 6 and Wheel II, andalso provide adjustable means for permitting the collar to rotate freelywhile preventing dust and grit from entering the journal bearing.

A sleeve I l, threaded internally and externally, is adjustably screwedon the reduced threaded end of housing E2, the forward or right-hand endof the sleeve I"! carrying a flange IQ of antifriction metal, againstwhich the rear face of the collar 7 runs.

On the external thread 29 of the sleeve H a cap, shown in detail in Fig.4, is screwed. This cap has an inwardly directed end flange 2i facedinside with an annular anti-friction washer 22 which engages the forwardface of collar i. Screw threads 23 provide for adjustably placing thewasher 22 against the forward face of the flange 1 so that the flangewill be prevented from moving in the direction of the length of thespindle.

A ring 24 is threaded on the reduced end of the housing l2 and serves asa lock-nut to keep the sleeve l1 and its associated parts locked intheir lengthwise adjusted position.

Tapered journal 6 is accurately formed, highly polished and preferablychromium plated. It fits as exactly into the tapered bushing Iii as iscommercially possible, the closeness of the fit being re'gulatable byshifting the spindle very slightly in the direction of its length. Thebearing surfaces are lubricated by a suitable oiler shown in Fig. 1, V

The endwise positioning of the tapered journal 6 is attained by shiftingthe fore-and-aift position of the spindle by means of its integralcollar '1. This is done by first loosening the looking ring 24, rotatingsleeve I! in the proper direction so that the flange [9 of sleeve IIwill clear the collar 1 and permit it to be moved corres'pondingly,thereby giving the desired closeness of a running fit between thejournal 6 and bushing ID. The collar 1 then can be held against theflange l9 in its proper running position by rotating the cap on itsscrew 23.

Thus fore and aft positioning of the spindle as a whole relatively tothe housing I2 is adjusted by means of the sleeve l1, and the spindle isheld in such position by the locking ring 24, the flange I9, and theflange 2| of the cap. Merely turning the ring 24 and the sleeve I!adjusts the tightness of the running fit at journal 6 without disturbingthe endwise thrust adjustment of collar I; or such thrust adjustment canbe altered by turning the cap without disturbing the adjustment of therunning fit.

Cylindrical journal 8 at the rear end of the spindle is, of itself,always free to move lengthwise, hence when the tapered journal 6 isbeing adjusted in the manner above described it will have no effect uponthe adjustment of the rear spindle bearing 8.

To keep the journal 8 centered, that is, coaxial with the spindle, andto prevent all sidewise play the flexible rear bushing 9, detailed inFig, 2, surrounds the journal 8. Bushing 9, which is tapered exteriorlyis received in the internally tapered fitting 15. It can be adjustedlengthwise of the fitting and lengthwise of the journal 8 by means ofthe rear cap 25 which is threaded at 26 onto the tapered fitting l5.When the cap is turned in the tightening direction on the fitting I5 ittakes against the end of member 9 and forces it toward the right, Fig.1, causing member 9 to contract and tighten around the journal 8.

The large rearward end of member 9 is externally threaded at 2'! toreceive a pull ring (not shown) whereby member 9 can be withdrawn fromthe tapered fitting l5 for inspection.

A groove 28 or internal channel is provided in the end washer 22 to,form an oil seal that preients dust from entering the bearing surfacesof collar 1 and journal 6.

By the means above described the grinding wheel is is kept in its truerotating plane 29 and is prevented from shifting in that plane; that isto say, the cutting rim 3!! of the wheel must run in a perfectly trueplane of revolution. over, there can not be any radial or tangentialjump or vibration at the periphery of the grinding zone which is at 30.

As has been stated, effective cutting action by the grinding wheel isdependent upon wearing away of the wheel itself, for if the wheel is notconstantly wearing away and thereby renewing the surface of its grindingzone its efficiency as a production unit is impaired. In order that theabrading surface of a grinding wheel may function in this essentialrespect the wheel must be relatively soft, as distinguished from what isknown as a hard grinding wheel. But obviously, softness of the wheelaccompanied by any vibration or jump in the motion of the wheel willresult in wavy or irregular places being formed on the operating zone ofthe abrading surface, necessitating constant correction by trueing upthe wheel, which in turn cuts down the daily output capacity of theoperator.

From the foregoing description of the structure and mode of operation ofmy improved precision spindle mounting it will be apparent that real andimportant difficulties have been entirely overcome and, for the firsttime in this art as far as I am aware, a thoroughly dependable,accurate, durable mounting has been provided for a precision grindingtool that can be easily adjusted and under all normal conditions of usewill lviorekeep the grinding wheel so exactly in condition of properrunning stability that soft grinding wheels can be employed and willyield greater production, give better work, and will effect importantsavings in the costs for upkeep and replacement of grinding wheels. Anoteworthy result is that a soft wheel, when used on this improvedspindle, will outwear and out-produce a so-called hard grinding wheel ofthe same size and design.

Another advantage is that larger diameter grinding wheels can be usedthan was possible without the wheel stability provided by myimprovement. Consequently work can be done faster on account of thehigher rim speed, and more difi'erent kinds of work can be done, forexample, accurate surfacing of flats, cylindrical or conical bosses, aswell as the shaping of the teeth of cutting tools such as described inthe foregoing specification.

claim and desire to secure by Letters Patent is:

In a precision grinding tool including a spindle having a grinding wheelon one end and a tapered journal and cylindrical journal, said spindlebeing rotatable in a tubular housing with bearings for said journals;having in combination, a fixed collar projecting peripherally from thespindle and situated beyond and spaced from the end of the housing andintermediate the said tapered bearing and the grinding wheel, a sleevethreaded adjustably on the end portion of the housing and having aninwardly projecting flange arranged to take against the rear face ofsaid collar, a screw cap adjustably threaded on said adjustable sleeveand having an inwardly directed flange taking against the forward faceof said collar; said cap and sleeve constituting means for adjusting therunning fit of the collar between the said flanges and for keeping thecollar and spindle from moving lengthwise; and

go also constituting means for adjusting the running Having thusdescribed my invention, what I fit of said tapered spindle in itsbearing.

ROLLIN M. SEVERANCE.

